Gas pressure actuated switch with calibration means



March 16, 1965 P. B. SAGAR 3,174,007

GAS PRESSURE ACTUATED SWITCH WITH CALIBRATION MEANS Filed March 12, 1962Fig. 7 Fig. 4

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PAUL B. SAGAR 5) BUCKHORM- CHEA THAM 8 BLORE AT TORNE YS United StatesPatent 3,174,007 GAS PRESSURE ACTUATED SWITCH WITH CALIBRATION MEANSPaul B. Sagar, 1331 SE. 51st Ave, Portland, Oreg. Filed Mar. 12, 1962,Ser. No. 179,177 Claims. (Cl. 200-813) My present invention comprises animprovement upon the structure disclosed and claimed in my prior PatentNo. 2,821,592, issued January 28, 1958.

The invention relates to a pressure actuated switch of the general typedisclosed and claimed in the aforesaid patent and more particularly toan improved switch having provision for compensating for out of levelmounting and for calibration of the switch. The general objects andadvantages of this type of switch are set forth in the aforesaid patent.

One object of the present invention is to provide for accommodating apivoted vane type switch to out of level conditions such as occasionedby sloping floors or upon which equipment may be mounted or the like sothat the switch may be utilized when the axis of the cylindrical passageof the switch is at a substantial inclination.

A further object of the present invention is to provide a simple,sturdy, inexpensive pivoted vane type of mercury switch in whichimproved means are provided for controlling the operating point of theswitch. A switch of this character may be employed to open or close acircuit such as an alarm circuit when the pressure differential betweenair within and without a space, or the pressure dilierential betweengasses in two different spaces, reaches a predetermined point, forexample .04 inch of water. By the present invention the switch may beadjusted to operate over a considerable range of pressure differentialsand such adjustment can be effected even though the casing for thepivoted operating vane thereof may be considerably out of level due toinaccuracies in mounting the switchon equipment or in mounting theequipment on a supporting structure.

A further object of the present invention is to provide a pressuredifferential switch of the foregoing character which may be easily andquickly calibrated after it is set into its position of use and theequipment for producing a pressure differential upon which the switch ismounted is set into operation. For example, one use of the pressuredifferential switch is to sound an alarm or otherwise actuate a signalif the filter of an air conditioning or heating system should becomeclogged to such an extent that the proper amount of air is not beingcirculated. When mounted in such a position with the equipment inoperation, the calibration mechanism of the switch of the presentinvention is readily accessible for adjustment.

The objects and advantages of the present invention may be more readilyunderstood by reference to the accompanying drawings taken in connectionwith the following specification in which like numerals refer to likeparts throughout, and in which two forms of the present invention aredescribed and illustrated.

In the drawings,

FIG. 1 is a vertical longitudinal section through a switch of thepresent invention, taken substantially along line 1--1 of FIG. 2;

FIG. 2 is a view of the right end of the structure of FIG. 1;

FIG. 3 is a partial vertical section taken substantially along line 33of FIG. 1;

FIG. 4 is a view in perspective of an actuating member forming a part ofthe structure of FIG. 1;

FIG. 5 is a vertical longitudinal section through a modified form ofswitch taken substantially along line 55 of FIG. 6;

3,174,007 Patented Mar. 16, 1965 FIG. 6 is a view of the right end ofthe structure of FIG. 5;

FIG. 7 is a view in perspective of an actuating member forming a part ofthe structure of FIG. 5; and

FIG. 8 is a schematic representation of an air conditioning systemhaving the present invention incorporated therein.

The air pressure actuated switch of FIGS. 1 to 4, inclusive, comprises asheet metal cylinder 10 forming a passage 12 bounded by the cylindricalinternal wall 14 of such cylinder. A disc 16 is pivotally mounted withinthe passage 12 by a bracket 18 clamped to the upper portion of theinterior of the passage by a screw 20. The bracket has a pair ofprojecting claws 22 thereon which extend through openings 24 in the discand are notched to provide a horizontal, transverse pivotal axisvertically spaced above the axis of the passage toward the top thereofso that the disc 16 freely swings within the passage. The disc 16 has adiameter less than the internal diameter of the passage, so that adifference of air pressure upon opposite sides of the disc will causeflow of air through the passage between the edge of the disc and thewall 14. The disc 16 has an elongated mercury switch tube 26 mountedtherein in which there is provided a drop of mercury 28 adapted to restat one end of the tube in an off position as illustrated, or to makecontact with terminals of leads 30 when the inclination of the tube isreversed. The mercury tube is mounted so as to project beyond one sideof the disc 16 to a greater extent than the other so that it and themercury therein :act as a counterweight tending to hold the disc in onedirecion of inclination from the vertical.

Leads 30 extend to a pair of posts 32 to enable the switch to be placedin a desired circuit. The posts 32 are mounted upon and insulated froman end plate 34 closing the end of the passage toward which the discinclines. A flange 36 on the end of the member 10 is soldered orotherwise affixed to the periphery of the plate 34, and a plurality ofmounting openings 38 are provided in the peripheral portion of the plate34 and of the flange 36 to enable the switch to be mounted upona'vertical member such as the wall 40 of the air conditioning systemillustrated in FIG. 8.

When the pressure differential between the opposite sides of the disc 16becomes sufficiently great, for example, by reason of an increase in thevacuum above the filter 42 of FIG. 8 when the amount of air capable ofpassing through the filter is reduced to such a point that the filtershould be cleaned or changed, the disc will swing inwardly to reversethe position of the mercury in the mercury tube switch, therebyenergizing a circuit such as the circuit illustrated including a signallight 44. In order to adjust the amount of such pressure differentialbetween the sides of the disc 16 for a given vacuum above the filter 42,the plate 34 is provided with an arcuate slot 46 of increasing widthfrom one end to the other through which air may flow from the spaceexternally of the air conditioning system. The effective area of suchslot may be varied by varying the position of a movable plate member 48pivoted to the plate 34. The plate 48 is fixed to a manually operablepositioning lever 50, the tip of which moves past calibrating indicia 52on the plate 34. Varying the effective size of the slot 46 varies thepressure drop produced by air passing through such slot and thereforevaries the pressure differential produced between the two sides of thedisc 16 for a given difference between the air pressure in the spaceabove the filter 42 and atmosphere pressure. The switch may thus becalibrated to act at different pressure differences.

Since it is not practical to always align the wall 40 or similar wallsof other type of equipment in which the present switch may be mounted soas to be absolutely vertical, it is obvious that the axis of the passage12 may vary from the horizontal, thereby varying the angle between theaxis of. the passage and the plane of the disc 16. In order that thespace around the disc and hence the pressure differential between theopposite sides of the disc resulting from flow of air through the devicemay remain substantially constant in spite of different degrees ofangularity of the disc with respect to the axis of the tube in itsnormal position, the disc is provided with a thickened edgediametrically opposed to its pivotal axis. This thickened edge may beprovided by forming the disc of two thin plates 54 in face-to-facerelation throughout the greater extent thereof, the lower portions ofwhich are divergent as indicated at 56. The thickened edge therebyprovided is at a maximum along the vertical centerline of the passageand progressively tapers toward the horizontal centerline of thepassage.

The modification disclosed in FIGS. 5, 6 and 7 includes a passageforming member 10 as previously disclosed, and a disc 60 which ispivotally mounted upon a transverse horizontal axis spaced from the axisof the passage toward the bottom thereof. The pivotal axis is providedby a bracket 62 having upwardly facing notched lugs 64 which engage inopenings 66 in the disc. A mercury tube switch 68 is mounted on the discand included in a circuit as previously described, in this instance theleads 70 going to posts '72 on a bracket 74 at the opposite end of themember 1d. The disc W is held tipped toward the right end of the passageby the counterweight effect of the overhanging mercury tube aspreviously described, and normally rests against the adjustable abutmentsuch as the screw 76 herein illustrated. The screw 76 passes through anend plate 8%) so that it may be adjusted from outside of the airconditioning space.

In order to adjust the pressure differential between the two sides ofthe disc 60 for a given total pressure differential between the ends ofthe device, the plate 86 is provided with a plurality of calibrationopenings 82 in each of which there is respectively mounted a removableplastic plug 84. By removing or replacing certain ones of the plugs 84the switch may be calibrated to act at various pressure differencesbetween the ends of the device. The disc 60 is provided with a thickenededge of the same characteristic as previously described by means of atapered flange 36 having its greatest Width at the top of the disc andtapering in both directions toward the horizontal diameter of the disc.The effective area for flow of air around the disc thus remainssubstantially constant even though the device is adjusted so that theangle of inclination of the disc relative to the cylinder 10 is changed.

The slot 46 and adjusting member 48, as well as the openings 82 and theremovable plugs 84, constitute variable orifice means at the end of thepassage toward which the switch disc normally inclines. Various otherforms of variable orifice means may be substituted therefor. Variousother forms of means may be provided to thicken the edge of the switchdisc. The disc 16 may be utilized in the switch of FIG. and a pair ofdiscs similar to the disc 60, if provided with opposing flanges, may beutilized in the switch of FIG. 1. Various other modifications such asdisclosed in my above-identified patent may be incorporated in a switchembodying the present invention. When I refer to air pressuredifferential and the movement of air, I mean a gas such as air.

Having illustrated and described various modifications of my invention,it should be apparent to those skilled in the art that the inventionpermits of modification in arrangement and detail. I claim as myinvention all such modifications as come within the true spirit andscope of the following claims.

I claim:

1. A gas pressure actuated switch comprising:

means having an internal wall forming a passage,

a vane pivotally mounted within said passage for swinging movement abouta horizontal pivotal axis vertically spaced from the axis of saidpassage and extending transversely of said passage,

said vane having an area less than the internal area of said passage toprovide for flow of gas through said passage so that a pressuredifferential is produced between opposite sides of said vane,

said vane having a thickened edge along a substantial portion of itsperimeter with its greatest thickness remote from the pivotal axis ofsaid vane and tapering to a minimum along the transverse edges of saidvane toward said pivotal axis so that the total clearance around thevane remains substantially constant while the vane swings through aconsiderable arc,

an elongated mercury switch tube mounted on said vane and projectinglaterally therefrom whereby to act as a counterweight tending to holdsaid vane in one direction from the vertical,

said vane being pivotally movable in the opposite direction to such anextent that the mercury in said switch tube reverses its effectiveposition when said pressure differential increases to a predeterminedvalue,

and variable orifice means at one end of the passage for producing anadjustable pressure drop due to said flow of fluid through said passageto adjust said pressure differential between the opposite sides of saidvane for a given total pressure difference across said switch.

2. The structure set forth in claim 1 wherein said pivotal axis is atthe top of said passage and said vane swings freely within said passage.

3. The structure set forth in claim 1 wherein said pivotal axis is atthe bottom of said passage and an adjustable abutment means is mountedwithin said passage toward the top thereof for adjustably limiting theswing ing movement of said vane in said one direction.

4. The structure set forth in claim 1 wherein said variable orificemeans comprises a plate extending across one end of said passage andhaving a slot therethrough and a movable membermounted on said plate andshiftable with respect thereto to vary the effective area of said slot.

5. The structure set forth in claim 1 wherein said variable orificemeans comprises a plate extending across one end of said passage, andhaving a plurality of openings therein and a plurality of removableplugs for selective positioning in said openings.

References Cited in the file of this patent UNITED STATES PATENTS2,821,592 Sagar Jan. 28, 1958 2,981,195 Payne et a1. Apr. 25, 1961FOREIGN PATENTS 581,478 France Sept. 29, 1924 743,763 Germany Jan. 3,1944

1. A GAS PRESSURE ACTUATED SWITCH COMPRISING: MEANS HAVING AN INTERNALWALL FORMING A PASSAGE, A VANE PIVOTALLY MOUNTED WITHIN SAID PASSAGE FORSWINGING MOVEMENT ABOUT A HORIZONTAL PIVOTAL AXIS VERTICALLY SPACED FROMTHE AXIS OF SAID PASSAGE AND EXTENDING TRANSVERSELY OF SAID PASSAGE,SAID VANE HAVING AN AREA LESS THAN THE INTERNAL AREA OF SAID PASSAGE TOPROVIDE FOR FLOW OF GAS THROUGH SAID PASSAGE SO THAT A PRESSUREDIFFERENTIAL IS PRODUCED BETWEEN OPPOSITE SIDES OF SAID VANE, SAID VANEHAVING A THICKENED EDGE ALONG A SUBSTANTIAL PORTION OF ITS PERIMETERWITH ITS GREATEST THICKNESS REMOTE FROM THE PIVOTAL AXIS OF SAID VANEAND TAPERING TO A MINIMUM ALONG THE TRANSVERSE EDGES OF SAID VANE TOWARDSAID PIVOTAL AXIS SO THAT THE TOTAL CLEARANCE AROUND THE VANE REMAINSSUBSTANTIALLY CONSTANT WHILE THE VANE SWINGS THROUGH A CONSIDERABLE ARC,AN ELONGATED MERCURY SWITCH TUBE MOUNTED ON SAID VANE AND PROJECTINGLATERALLY THEREFROM WHEREBY TO ACT AS A COUNTERWEIGHT TENDING TO HOLDSAID VANE IN ONE DIRECTION FROM THE VERTICAL, SAID VANE BEING PIVOTALLYMOVABLE IN THE OPPOSITE DIRECTION TO SUCH AN EXTENT THAT THE MERCURY INSAID SWITCH TUBE REVERSES ITS EFFECTIVE POSITION WHEN SAID PRESSUREDIFFERENTIAL INCREASES TO A PREDETERMINED VALUE, AND VARIABLE ORIFICEMEANS AT ONE END OF THE PASSAGE FOR PRODUCING AN ADJUSTABLE PRESSUREDROP DUE TO SAID FLOW OF FLUID THROUGH SAID PASSAGE TO ADJUST SAIDPRESSURE DIFFERENTIAL BETWEEN THE OPPOSITE SIDES OF SAID VANE FOR AGIVEN TOTAL PRESSURE DIFFERENCE ACROSS SAID SWITCH.